c^2 Journal of Agricultural Research Voi.vi.No. 14 



times, with additions of carbon-dioxid-free water. The total alcohols found were 

 calculated as ethyl alcohol. 



Aeration method: In this method a current of air was drawn through the alcohol 

 solution, which was saturated with ammonium sulphate, into concentrated sulphuric 

 acid. The sulphuric-acid solution was then oxidized with potassium-dichromate 

 solution and distilled as before. 



Amino nitrogen. — The amino nitrogen was determined on the diluted juice with 

 the Van Slyke apparatus. 1 



Moisture. — The moisture content was determined by heating a sample of about 

 100 gm. in an oven at ioo° C. 



DISCUSSION 



The determinations of total acidity, volatile acidity, total alcohols, and 

 amino nitrogen furnish a measure of the most characteristic changes which 

 take place in silage fermentation and a partially complete picture of the 

 character of the fermentation and the character of the silage, as nearly as 

 chemical analysis can show. This, the ordinary estimations of crude pro- 

 tein, fiber, ether extract, and ash fail to do. The amount of amino nitrogen 

 is, of course, of comparative value only, but it shows the degree of hydro- 

 lysis of protein. Unfortunately in this case no figures are now available for 

 the amino nitrogen of green rape. The results given in Table I, however, 

 indicate that the degree of hydrolysis of protein was nearly the same in 

 each sample upon which this determination was made. The total acidity 

 was quite similar in each of the samples which were classed "A" and 

 " B." The total acidity of the silage juice in most cases is no higher than 

 the average acidity of corn-silage juice. The average of analyses on 100 

 c. c. of juice of several samples of normal corn silage is as follows: 



Total acidity ' 271 c. c. of Njio solution. 



Volatile acidity 91 c. c. of N/io solution. 



Alcohol o. 312 gm. 



Amino nitrogen o. 109 gm. 



The explanation of the very sour taste of rape silage may lie in the 

 fact that it has a much higher water content than corn silage and thus 

 affects the nerves of taste more quickly. A considerable amount of 

 sulphates was found in one sample, but the presence of any free mineral 

 acid could not be demonstrated. The volatile acidity seemed to vary 

 more widely, with varying experimental conditions. The alcohol con- 

 tent was probably small in all cases where there was no addition of 

 sugar. In two cases of silage with added sugar or molasses Table I 

 shows that an abnormally large amount of alcohol was found. This, 

 as well as the increased acidity, militates against the addition of molasses 

 to silage materials. It is very probable that the excess alcohol was 

 formed after the maximum acidity had been reached and the yeasts had 

 gained the ascendancy. 



1 Van Slyke, D. D. The quantitative determination of aliphatic amino groups, II. In Jour. Biol. Chem., 

 v. 12, no. 2, p. 275-284, 1 fig., 1 pi., 1 tab. 1912. 



